Human knowledge, walked from classification system to knowledge graph.

Economic and trade taxonomies: HS (Harmonised System) is the World Customs Organisation 6-digit international product nomenclature with national 8-10 digit extensions — covers virtually all merchandise trade globally; the WCO HS 2022 edition is the current revision with HS 2027 in development. NAICS (North American Industry Classification System) replaced the old SIC codes for US/Canada/Mexico statistics. NACE (EU equivalent), ISIC (UN Industrial Classification), ANZSIC (Australia/NZ), NIC (Indian National Industrial Classification). The platform documents cross-walks between HS, NAICS, ISIC, NACE for trade-and-industry analysis.

Geographic and population taxonomies: ISO 3166 (country codes alpha-2, alpha-3, numeric — the foundation of nearly all cross-border data systems), ISO 639 (language codes), ISO 4217 (currency codes), UN M.49 (region codes), NUTS (EU regional classification), FIPS (US federal), UN/LOCODE (location codes for ports / inland points), GeoNames (the open-data populated-place database with around 12M place names), OSM features (the OpenStreetMap typology). Demographic taxonomies: ICD-related cause-of-death classification for vital registration; ISCO (International Standard Classification of Occupations) for labour-market data; ISCED (International Standard Classification of Education) for cross-border education comparison.

The encyclopedic discipline distinguishes itself from open-content via signed expert authorship (the SEP entry on a topic is written by an acknowledged specialist), explicit editorial review, citation rigor, and version stability with archived prior versions. SEP's technology is particularly notable: every entry is dated, has an explicit table of contents, footnotes are full bibliographic, and the entry is archived on every substantive update. Comparison with Wikipedia: SEP has approximately 1,800 entries (curated philosophy); Britannica has approximately 120,000 entries; Wikipedia has around 6.8M English articles — the trade-off is breadth-versus-curation, with the platform's recommendation that policy-grade or research-grade citation should generally use signed-and-dated encyclopedic sources rather than collaborative-editing platforms.

Specialist reference works: medical reference (Harrison's Principles of Internal Medicine, Goodman & Gilman's Pharmacological Basis, Williams Hematology, Robbins Pathology — the serial-edition standards), legal (Halsbury's Laws of England, Restatement of the Law US, Cornell Legal Information Institute, India Code, Singapore AGC database), economic / financial (Palgrave Macmillan New Palgrave Dictionary of Economics, IMF Glossary of Selected Financial Terms, BIS / FSB / IOSCO documents), statistical (UN Statistics Division glossaries, OECD Statistical Methods Compendium, ESS standards). Translation reference: bilingual / multilingual specialist dictionaries (the EU IATE, the FAO terminology portal, ISO terminology standards). The platform's reference-discipline emphasises locating an authority source rather than relying on aggregated content.

OpenStreetMap (OSM) is the open-content global geographic database, founded 2004; over 10M registered contributors; daily diff-and-history publication; the foundation underneath Apple Maps (extensive OSM use post-2018), Facebook Maps, Snap Map, Foursquare, MapBox, MapTiler, and many open-source geocoders. The OSM data model uses nodes / ways / relations with arbitrary tagging governed by community consensus rather than fixed schema. Coverage quality ranges from comprehensive (Western Europe, North America, Japan, India urban) to sparse (much of rural Africa, parts of Central Asia) — with HOT (Humanitarian OpenStreetMap Team) coordinated mapping in disaster-response and underserved-area projects.

Open-content libraries: Project Gutenberg (public-domain ebooks, founded 1971, around 70K titles), Internet Archive (founded 1996; the Wayback Machine archives over 800 billion web pages, plus IA Books / Audio / TV / Software / Open Library / Scholar; the controversial Controlled Digital Lending lawsuit by publisher consortium 2023 was lost by IA on initial ruling, with appeal continuing), HathiTrust (academic-library digitisation consortium), Europeana (EU cultural-heritage aggregator), DPLA (Digital Public Library of America), Trove (National Library of Australia), National Digital Library of India (NDLI). OpenLibrary, WorldCat (the OCLC catalogue with 500M+ records), BHL (Biodiversity Heritage Library) round out the major open-knowledge layer. The platform documents licensing and attribution requirements for reusing each source.

Preprint servers have transformed dissemination speed in many fields. arXiv (founded 1991 at LANL, now Cornell-hosted): the foundational preprint server for physics / mathematics / computer science / quantitative biology / quantitative finance / statistics; over 2M papers; daily new postings drive the conversation in many sub-fields. bioRxiv (Cold Spring Harbor; biology), medRxiv (medicine; the COVID-era surge was disciplinary turning-point), SSRN (Elsevier-owned; social sciences and humanities), Research Square, ChemRxiv, EarthArXiv, PsyArXiv. The platform documents preprint-citation conventions: emerging consensus toward citing preprint plus DOI plus version, and toward formal preprint-to-publication chain-of-record disclosure.

Open Access (OA) and Plan S: the mandate originating with cOAlition S funders (initially Wellcome, ERC, FNR, etc.) requires Plan S compliance for funded research output; transformative agreements (read-and-publish deals) between universities and commercial publishers have substantially shifted Europe's journal-economics. OA models: gold (publisher-side OA with article-processing-charges), green (author-self-archived in repository), diamond (no-fee OA, often via society or scholar-led journals like the SciELO network in Latin America). Predatory journals: Beall's List historical legacy, Cabells Predatory Reports current commercial offering, DOAJ inclusion-criteria tightening, plus retraction-tracking via Retraction Watch; the platform's academic-source filtering criteria are explicit in /methodology/.

Discipline-specific databases: IEEE Xplore (electrical / electronics / computing), ACM Digital Library (computing), SciFinder / CAS (chemistry / pharmaceutical patents), MathSciNet (American Mathematical Society), zbMATH (European Mathematical Society), INSPIRE-HEP (high-energy physics), NASA ADS (astrophysics), SPIE Digital Library (optics / photonics), EconLit (American Economic Association; economics indexing), RePEc (open-economics; the Federal Reserve Bank of Saint Louis FRED-related repository), SSRN (overlapping preprint-and-database role for social science), JSTOR (Andrew W. Mellon Foundation; arts / humanities backfile).

Citation metrics and bibliometrics: JIF (Journal Impact Factor) — the most-cited but most-criticised metric; 2-year window of citations / publications; field-comparison-distorted; field-normalised alternatives (FWCI, SNIP) emerged in response. h-index (Hirsch 2005; balances productivity and impact) is the dominant per-author metric. SCImago SJR, SNIP (CWTS), Eigenfactor (PageRank-style for journals), Altmetric (social-media + policy + news mentions). DORA (Declaration on Research Assessment): signed by major funders / institutions / publishers; pushes back against single-metric (JIF) evaluation; pushes for content-evaluation and broader contribution-recognition. The platform's scholarship-citation discipline aligns to DORA principles.

Web and software standards: W3C (World Wide Web Consortium) — HTML, CSS, SVG, XML, RDF, OWL, accessibility (WCAG), the entire web-platform. WHATWG (parallel HTML/DOM Living Standards process). Ecma International (ECMAScript / JavaScript via ECMA-262, JSON via ECMA-404). Unicode Consortium (Unicode Standard, Unicode 16 current; CLDR locale data). Khronos Group (OpenGL, Vulkan, OpenCL, glTF). Bluetooth SIG, Wi-Fi Alliance, USB-IF, Trusted Computing Group, 3GPP (cellular generations 4G LTE, 5G, 6G research) are the major industry-consortium standards bodies. The platform indexes standard-track and spec-stage by major technology area.

Sector-specific standards: Codex Alimentarius (FAO/WHO joint — food safety standards globally), OIE / WOAH (animal health), IPPC (plant health), ICAO Annexes (aviation), IMO conventions (maritime — SOLAS, MARPOL, STCW), OIML (legal metrology), BIPM / CGPM / SI (units of measurement), ICH (International Council for Harmonisation — pharmaceutical regulation). Industry-association standards: API (American Petroleum Institute), ASME (mechanical engineering), ASTM International (materials testing), AISC (steel construction), ACI (concrete). The platform documents the WTO TBT Agreement reference: international standards take precedence as legitimate-basis for regulatory measures, making standards-body output economically consequential.

Prior-art search and examination: USPTO PAIR, EPO Espacenet (free; over 140M global patent documents), WIPO PATENTSCOPE, Google Patents (full-text search across major offices), Lens.org (open-data patent intelligence), Derwent World Patents Index (Clarivate commercial), Orbit Intelligence (Questel commercial). Patent classification: IPC (International Patent Classification, WIPO), CPC (Cooperative Patent Classification, USPTO+EPO joint), Japanese FI / F-term, Locarno (designs). Patent families: INPADOC, DOCDB, simple family vs extended family methodology — relevant for understanding global filing strategies.

Specific regimes and practical issues: SEPs (Standard-Essential Patents): FRAND (fair, reasonable, non-discriminatory) licensing obligations for SEPs declared to standards bodies (3GPP, ETSI, IEEE) — the central commercial-IP friction in mobile, video-codec (H.264, HEVC, VVC, AV1 royalty-free counter-stack), Wi-Fi, Bluetooth standards. Patent thickets and pools: MPEG LA, Sisvel, Avanci, HEVC Advance the major commercial pools. Compulsory licensing under TRIPS Article 31 (active in HIV/AIDS antiretrovirals historically; pandemic-period proposals; Indian and Brazilian compulsory-licensing precedents). Defensive publication: Research Disclosure, IP.com, Google Cloud open-source patent commitments — alternatives to patenting that establish prior-art without seeking exclusive rights.

Vital records and civil registration: birth / marriage / death registration regimes vary widely. Strong-coverage economies (most of Europe, Anglo-settler economies, Japan, Korea, much of Latin America) have effectively-universal vital registration with multi-decade backfile. Coverage gaps: many lower-income economies still have substantial under-registration; CRVS (Civil Registration and Vital Statistics) programmes by WHO / UNICEF / UNFPA / World Bank coordinate strengthening. Genealogical research: FamilySearch (LDS Church-operated; the world's largest free genealogy resource with 14B+ records and growing microfilm-digitisation), Ancestry.com (commercial; AncestryDNA leading consumer-genetic genealogy), FindMyPast (UK / Irish / Australian focus), MyHeritage, 23andMe, Geni. Specialist archives: shoah / holocaust archives (USHMM, Yad Vashem, Wiener Holocaust Library), South African TRC archive, Khmer Rouge documents (DC-Cam, Tuol Sleng), Stasi files (BStU then federal-archive).

Records-retention regimes for businesses and individuals: tax records: typically 7+ years US (with up to 10 for substantial-omission cases), 6 years UK (with longer for VAT and corporation tax under specific circumstances), 8 years India (Section 143(2) and reassessment provisions), 7 years EU GDPR generally permits but specific sectoral rules vary. HR records: 7 years US (federal minimum; state may extend), 6 years UK. Medical records: 25-30 years typical for adult care; longer for pediatrics. Building records: lifetime-of-building plus 12 years typical UK. Corporate records: indefinite for incorporation / share-issue documents, 6+ years for board minutes most jurisdictions. The platform's records-retention table indexes by record-type, jurisdiction, and statutory basis.

Web archiving: Internet Archive Wayback Machine archives over 800B web captures; Common Crawl open-data web crawl (around 250B pages); Archive-It (IA service for institutional collections). National web archives: UK Web Archive (BL), French BNF web-legal-deposit, Library of Congress web archive, Australian PANDORA / AWA, Indian NDLI components. Digital legal deposit: many jurisdictions have extended legal-deposit obligations from print to digital materials post-2010. Personal-archiving tools: ArchiveBox (open-source), SingleFile, Pinboard, Memex, Web Archive, archive.today (commercial alternative to IA). The platform's recommendation: archive every external citation in serious knowledge work to prevent link-rot — substantial empirical-research evidence shows 30-50% link-rot within 5 years for general web content.

Format and metadata standards: METS (Metadata Encoding and Transmission Standard), PREMIS (Preservation Metadata Implementation Strategies) — the core preservation-metadata frameworks. File-format obsolescence: open and well-documented formats (PDF/A, plain text, TIFF baseline, FLAC, WARC) preferred for preservation; proprietary single-vendor formats (older AutoCAD, older Pro Tools, older Microsoft Office binary) are migration risks. Format-migration tools (UDFR, PRONOM signature library, JHOVE / FITS validators); emulation as alternative-or-complement to migration (the Internet Archive emulator collections demonstrate the principle for software / games preservation). Bit-rot: hardware media half-life concerns drive periodic refresh-and-checksumming (BagIt manifest, fixity-checks); the platform's digital-preservation guides cover practical workflows for individual / small-organisation / large-institution scales.

Semantic Web stack and standards: RDF (Resource Description Framework) — W3C standard; the data model. RDF Schema, OWL (Web Ontology Language) — ontology layers. SPARQL — query language. SHACL — shape constraints. JSON-LD — the JSON-encoded RDF flavour increasingly used for embedded structured-data on the web (Google adopting JSON-LD as its preferred Schema.org delivery mechanism; Schema.org markup is now near-universal in major-publisher SEO). SKOS — Simple Knowledge Organisation System for thesauri / taxonomies. Linked Open Data (LOD) cloud: visualisation of cross-linked datasets — from a few dozen datasets at LOD inception (2007) to over 1,300 datasets currently catalogued.

Major ontologies and vocabularies: Schema.org (Google + Microsoft + Yahoo + Yandex; over 800 types and 1,400 properties; the de-facto SEO-relevant entity vocabulary). FOAF (Friend-of-a-Friend): people / social. SIOC: online communities. Dublin Core: metadata baseline. BIBFRAME: bibliographic (Library of Congress; eventual MARC successor). FIBO (Financial Industry Business Ontology). Gene Ontology (GO): biology. SNOMED CT, LOINC, RxNorm: clinical. ICD-O: oncology. NASA SWEET: earth science. QUDT: units / measurement. PROV: provenance. schema.org / DataCommons / OpenAlex / OpenStreetMap are the open-data backbone now feeding LLM training corpora — making knowledge-graph hygiene a frontier-AI input variable.